The present invention relates to a method for storing evaporated radioactive waste concentrates mixed with bitumen where water has been expelled from the wastes by heating to temperatures above the boiling point of water and subsequently filling the mixture into suitable containers, and to a suitable discharge device therefor.
The object of conditioning radioactive concentrates from waste water processing is to bring the end product into a storable, i.e. a water insoluble, form. In addition to mixing the wastes with cement, a fixing process employs the much more advantageous embedding of the aqueous concentrates or muds and resins, respectively, in hot bitumen.
In this bituminization process the muds or concentrates are introduced into bitumen above 140.degree. C. by means of a multiple shaft extruder in which the water evaporates and the radioactive salts are mixed with the bitumen. The mixture of bitumen and waste leaves the worm shaft extruder under its own gravity force through an open channel into an available drum or waste container. The extruder acts as the evaporator and the mixture is at a temperature of 160.degree.-170.degree. when it leaves the extruder. Due to the low viscosity required, the temperature must be correspondingly high.
The particular drawback of this arrangement is that the bitumen-waste mixture is exposed to the atmosphere while at a high temperature, which involves great danger of combustion. The open discharge channel may also easily become clogged since the stream of bitumen and waste does not flow homogeneously and uniformly. This then requires intensive monitoring of the filling process.